Today incredible images were beamed around the world of civilians walking in space – for the very first time. All eyes were on businessman Jared Isaacman and engineer Sarah Gillis as they ventured outside a Space X capsule. But is this an historic space exploration milestone - or just a very exciting holiday for a billionaire? We'll find out more from the BBC’s own expert space-watcher Jonathan Amos. Also this week, we visit Sellafield which processes and stores more radioactive material per square metre than any other site in Europe. But it is getting full. So where is our nuclear waste going to go in future? As the UK searches for a new potential site, we look at the science of what we do with nuclear waste and why. We’ll also delve into the fascinating world of nuclear semiotics. How can we communicate the dangers of nuclear waste to people living 100,000 years from now? Presenter: Vic Gill Producers: Sophie Ormiston & Gerry Holt Editor: Martin Smith Studio manager: Cath McGhee Production Co-ordinator: Andrew Rhys Lewis